Laboratory Evaluation for
A Green, Guided-Inquiry Based Electrophilic Aromatic Substitution for the Organic
Chemistry Laboratory
Source: Eby, E.; Deal, S. T. J. Chem. Educ., Print 2008, 85, pp 1426-1428.
Date: June 2009
Submitted by Kailey Luoma, Josh Camreta, and Devin Stucki, students at Central Oregon
Community College in Bend, Oregon.
Evaluation
The purpose of this lab is to iodinate salicylamide through electophilic substitution. Salicylamide
has an activating group (OH) and a deactivating group (CONH2) already attached. Predicting
whether the iodination occurs at an ortho/para position or meta position helps reinforce
understanding of electrophilic substitution and the characteristics of aromatic molecules. Over
all, this lab provides students with several opportunities to develop different laboratory skills
including infrared spectrometry, pH testing, vacuum filtration and recrystallization. The solution
undergoes several color changes making it possible to visually see chemical changes taking
place, which made it appealing to students.
This lab provided a very straightforward experiment to determine the directing effects of groups
on an aromatic ring upon the addition of iodine. The final placement of iodine on the aromatic
ring is identified using infrared spectrometry.
The lab procedure seemed very easy to follow and presented directions that helped walk the
student through each step, without causing confusion. One problem arose when the solution
didn't reach the faint, pale yellow color it was supposed to, but instead remained a bright green.
A color change usually signifies a chemical change. Conversely the lack of a complete color
change may show that the reaction didn't proceed as was intended. This may have occurred if
the amount of sodium hypochlorite solution added was too small to react with all of the
salicylamide and sodium iodide. More sodium hypochlorite than the procedure states may need
to be added in order to push the reaction to the desired color. In spite of the color differences,
the product was determined to be the expected 1,2,4-trisubstituted aromatic molecule.
Although this lab uses several toxic materials, like HCl and Sodium hypochlorite, they are used
in dilute and small quantities. The toxicity of these chemicals in a dilute state is minimal. There
are no major disposal concerns for these materials.
This is a good lab for introducing electrophilic aromatic substitution and green chemistry. The
procedure is simple, easy to follow, and appears to be effective. It is very useful for reinforcing
skills of interpreting infrared spectrograph, as the students have to identify the location of the
iodide on the aromatic molecule. 1H NMR would be a very useful tool in identifying this product,
but infrared works well also.
Experiment: A Green, Guided-Inquiry Based Electrophilic Aromatic Substitution for the Organic Chemistry
Laboratory
1
Evaluation Procedure: This evaluation was part of a class assignment for the organic
chemistry laboratory. Students were asked to identify, field-test and evaluate a laboratory listed
in the GEMs database (http://greenchem.uoregon.edu/gems.html). Activities included out of
class meetings, laboratory testing sessions and collaborative development of their evaluations
using a Wiki. Laboratories were selected based on their suitability for the Organic curriculum as
well as on their ability to effectively introduce green chemistry principles. Evaluations include
commentary about the procedure from a student’s perspective.
Faculty Advisor and Contact
Carol Higginbotham
Professor of Chemistry
Science Department
Central Oregon Community College
2600 NW College Way
Bend, OR 97701
Email= chigginbotham@cocc.edu
Phone= 541-383-7552
Experiment: A Green, Guided-Inquiry Based Electrophilic Aromatic Substitution for the Organic Chemistry
Laboratory
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